The present invention relates to radio frequency identification (RFID) tag systems and more particularly to an RFID tag system that employs a chargeable ink as a power source.
Remote electronic identification devices have been employed in a variety of industries. For example, stores place RFID tags on articles of clothing and other types of goods. An unauthorized removal of a good carrying an RFID tag causes a signal to be transmitted to an electronic security system. The RFID tag will receive a signal from the electronic security system placed near an exit, and transmit a response informing the electronic security system of the presence of an article being passed through the electronic security system and removed from the store. An alarm can then be invoked to inform store personnel that an article is being removed without authorization. Additionally, RFID tags have been employed in warehouses and other businesses to ensure accurate inventory counts. RFID tags have also been utilized in performing inventory counts in trucks and other vehicles.
There are two different types of remote electronic devices. The first type is known as an active RFID system and the second type is known as a passive RFID system. An active RFID system includes a battery powered transponder (i.e., a receiver and a transmitter), which can receive signals from a base station or interrogator and transmit identification information back to the interrogator. A passive RFID systems receives its power directly from the base station or interrogator and typically stores this power in a storage device. The power allows for the passive RFID system to transmit identification information to the base station or interrogator. The problem with the passive RFID system is that it has limited power transmission capabilities. Typically, the passive RFID system can only transmit identification information to a range of about two feet. Additionally, the passive RFID system can only store the power received by the interrogator for two to three seconds. Active RFID systems transmit identification information at a much higher range and can store energy as long as the battery remains at a charge level high enough to transmit. However, active RFID systems are much larger and more unsightly than passive RFID systems.
Accordingly, there is a strong need in the art for an RFID tag having the transmission power of an active RFID tag, while retaining the advantages of a passive RFID tag.
According to a preferred aspect of the invention, an RFID tag system is provided that is convertable from a passive system to an active system. Capacitive wells are provided on the. RFID tag system that can retain energy for a period of about 24 hours. The capacitive wells provide power to the active components on the RFID tag system for reception and communication of messages between the RFID tag system and a base unit. Preferably, the capacitive wells are formed by printing a conductive ink onto the RFID tag system. The conductive ink forms a capacitive well having stored up energy upon charging of the conductive ink. Present passive RFID tags can be provided on paper thin labels with active components embossed therein. Chargeable ink can be printed onto printable regions on the back or front of the labels. Interconnects and contacts connect the chargeable ink to the active components on the RFID tag system. The ink can be charged prior to printing on the RFID tag system or charged after the ink is printed onto the RFID tag system. The printed wells can be formed similar to large capacitive plates. The capacitive wells can also be formed from printed features such as a barcode or such as group of alphanumeric characters. The printed features can also provide the RFID tags with a human or machine readable features in addition to providing the RFID tag with a capacitive well.
Thus, according to one aspect of the present invention, an RFID tag system is provided. The RFID tag system comprises an active component module, a transceiver module coupled to the active component module and a chargeable ink well printed on the RFID tag system. The chargeable ink well is adapted to provide power to the active component module and the transceiver module. The chargeable ink well can be charged prior to or after it is printed on the RFID tag system. A recharge system can be provided on the RFID tag system for charging or recharging the chargeable ink well. Preferably, the RFID tag system is shaped like a label having a front side and a rear side. The chargeable ink well can be printed on the rear or front of the label. The chargeable ink well can include any printable feature or combination of printable features, such as a printed plates, barcode labels and/or alphanumeric characters.
In accordance with another aspect of the present invention, a method of forming an RFID tag system is provided. The method comprises the steps of providing an RFID tag having components for transmitting and receiving messages and printing a printable feature with a chargeable ink on an RFID tag. The printable feature is coupled to the components for providing power to the components. The chargeable ink well can be charged prior to or after the step of printing the chargeable ink well on the RFID tag system. In one aspect of the invention, the chargeable ink well is charged by providing a magnetic field. In another aspect of the invention, the chargeable ink is charged by providing a power transmission signal. The chargeable ink well can include any printable feature or combination of printable features, such as a printed plates, barcode labels and/or alphanumeric characters.
In accordance with yet another aspect of the present invention, an RFID tag system is provided. The RFID tag system comprises means for transmitting and receiving messages and a chargeable ink well printed on the RFID tag system. The RFID tag system can include means for receiving and harnessing a charge signal to charge the chargeable ink. The RFID tag system can also include means for storing RFID tag system identification information.